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Abstract

Forest growth predictions are used to build expectations about the
future economic performance of management decisions. Faustmann
land expectation value (LEV) is a widely used criterion in forestry
to evaluate a diversity of decision parameters, such as rotation age
and thinning regimes. Most of the predictions and, consequently,
expectations are based on emperical knowledge, assuming a steady
state in climate and a deterministic forest growth approach. However,
the climate may change to potentially different degrees in the
coming decades, causing a dynamic and uncertain forest growth
and carbon budget. Moreover, carbon economy in forestry, defined
as opportunity cost of in situ carbon sequestration, can hardly
be analysed using empirical models and calls for process-based
forest biomass production models. Process-based models include
numerous parameters and processes that embody some degree of
uncertainty. The uncertainty of these parameters and climate state
propagates over time to the final decision about carbon economy
and optimal management solutions. Here we quantify this uncertainty
using Bayesian inference and apply twelve different climate
change scenarios to evaluate the forecasts of the process-based
forest model 3-PG, to predict the growth of European beech (Fagus
Sylvatica) in central european conditions as an example. The results
show a strong influence of the model’s parameters uncertainty
on the final decisions about timber based and carbon economy.
The uncertainty triples if different climate change scenarios are
applied as a source of deep uncertainty where no probability can be
assigned to any scenario. To deal with deep uncertainty, a robust
decision-making approach has been applied to find solutions with
minimum regret or maximum value at risk regarding all scenarios.
We conclude that communicating uncertainty is a fundamental
issue for forestry economics under changing climate conditions,
especially if carbon sequestration is an asset. The key message for
designing global forest governance policy in the uncertain times of
climate change will be the necessity to take into account both the
uncertainty on the demand side, that is, socio-economic developments
and regional population needs for forest ecosystem services
such as wood, but also the uncertainty of the supply side and the
inherent ecological uncertainties in predicting the forests’ growth,
resources, and climatic conditions.